The present invention is related to microfluidic devices and methods of using the same. More specifically, the present inventions provides a microfluidic device with a monolithic microwave integrated circuit and methods of using the same.
There has been tremendous growth over the past several years in the fabrication of microfluidic devices. Monolithic microfabrication technology now permits the assembly of a multiplicity of different devices in one compact, interconnected system. For example, individual microfluidic accessories such as mixers, micro-contactors, reactors, pumps, valves, heaters, mixers and species detectors for microliter to nanoliter quantities of solids, liquids and gases may be integrated into a substrate containing microfluidic channels connecting such components to form a microfluidic device. Integrated microinstruments may be applied to biochemical, inorganic, or organic chemical reactions to perform biomedical and environmental diagnostics, and biotechnological processing and detection. Integrated microfabricated devices can be manufactured in batch quantities with high precision, yet low cost, thereby making recyclable and/or disposable single-use devices practical. Alternatively, the instrument may consist of an array of reaction instruments, which operate in parallel to simultaneously perform a number of related reactions. Operation of such instruments is easily automated, further reducing costs. Since the analysis can be performed in situ, the likelihood of contamination is very low.
Microstructure technology offers distinct advantages over macroscale technology, including the ability to perform efficient and rapid chemical analyses at a lower cost per analysis, because of decreased sample volume requirements and increased throughput. Thermocycling of these smaller volumes/masses is much more rapid, and requires much lower power input. Small volumes and high surface-area to volume ratios provide microfabricated reaction instruments with a high level of control of the parameters of a reaction. In addition, small sample volumes are advantageous because they allow a user to perform multiple analyses in parallel using a single sample on a single chip. Smaller sample volumes are also advantageous in instances where the amount of material is limiting.
Some researchers have employed microfabrication techniques in the miniaturization of processes involved in biochemistry/biomedical testing, for example nucleic acid amplification. There is a significant trend to reduce the size of these sensors, both for sensitivity and to reduce reagent costs. Thus, a number of microfluidic devices have been developed, generally comprising a solid support with microchannels, utilizing a number of different wells, pumps, reaction chambers, and the like. See for example EP 0637996 B1; EP 0637998 B1; WO96/39260; WO97/16835; WO98/13683; WO97/16561; WO97/43629; WO96/39252; WO96115576; W096/15450; WO97/37755; and WO97/27324; and U.S. Pat. Nos. 5,304,487; 5,071531; 5,061,336; 5,747,169; 5,296,375; 5,110,745; 5,587,128; 5,498,392; 5,643,738; 5,750,015; 5,726,026; 5,35,358; 5,126,022; 5,770,029; 5,631,337; 5,569,364; 5,135,627; 5,632,876; 5,593,838; 5,585,069; 5,637,469; 5,486,335; 5,755,942; 5,681,484; and 5,603,351, all of which are expressly incorporated herein by reference.
In particular, U.S. Pat. No. 5,639,423, to Northrup et al., incorporated herein by reference in its entirety for all purposes, describe an integrated micro fabricated device for amplification of previously extracted nucleic acid by polymerase chain reaction (PCR). Northrup et al. describe lysing target cells and separating the nucleic acid from the lysate by standard macroscopic techniques. The separated nucleic acid is introduced into a reaction chamber in the microstructure and appropriate PCR reagents are added thereto via a series of micro pumps, microchannels and micro valves. Thermocycling for PCR amplification is accomplished by resistive heating elements incorporated into the microdevice and adjacent to the reaction chamber. Resistive heating has several disadvantages. The resistive element and its surrounding thermally conductive material retains energy, which will continue to heat the sample even after the power is shut down to the element. Additionally, heat transfer depends substantially on passive conduction mechanisms.
Microstructures have also been described to accomplish cell lysis with and without PCR amplification. U.S. Pat. No. 5,304,487 to Wilding et al., incorporated herein by reference in its entirety for all purposes, discusses the use of physical protrusions within microchannels or sharp edged particles within a chamber or channel to mechanically lyse the cell, after which the lysate is tested (to determine what type of cell is present for example). Waters et al. describe thermally lysing cells in a micro-reaction chamber containing the PCR amplification reagents by heating the entire device in a commercial thermocycler. Waters et al., Microchip Device for Cell Lysis, Multiplex PCR Amplification, and Electrophoretic Sizing, Anal. Chem 70:158-162 (1998) (incorporated herein by reference). The entire device is then thermocyled to amplify the nucleic acid within the lysate, after which an intercalating dye is added. The amplified nucleic acid lysate solution is then loaded from the micro-reaction chamber onto a micro-electrophoretic sizing column, which is connected by a micro valve to the lysing/PCR reaction chamber, and the nucleic acid contents within the lysate are sized.
On the macroscopic scale, nucleic acid extraction can be accomplished in a number of different ways, for example, mechanical, chemical, enzymatic, thermal or any combination thereof. Several researchers have reported that exposing cells to microwave radiation in combination with other extraction techniques enhances nucleic acid extraction from cells and virus and shortens the time required therefore. For example, Hultner and Cleaver (hereinafter Hultner et al.) exposed cells, resuspended in 400 xcexcL of STET/lysozyme buffer solution, to microwave radiation. A Bacterial Plasmid DNA Miniprep Using Microwave Lysis, Bio Techniques 6:990-993 (1994). Hultner et al. further report that 15-20 seconds of microwave exposure was sufficient to achieve plasmid recovery compared to 40 seconds using the more conventional boiling-lysis method, and that applying microwave radiation achieved more reliable (i.e., lower failure rate) results. Id. Goodwin and Lee (hereinafter Goodwin et al.) applied microwave plasmid radiation for approximately 30 seconds to eukaryotic cells in a standard volume of lysis buffer, added additional lysis buffer, and incubated the resulting solution for 10 minutes. Goodwin et al. report that this method achieved results comparable to the standard more laborious methods, and reduced incubation times to approximately 10 minutes from approximately an hour in the other methods. Jones et al. used microwave irradiation in the filter lysis technique and demonstrated that 51 of 59 bacterial species yielded genetic material detectable by standard nucleic acid hybridization techniques. An Oligonucleotide Probe to Assay Lysis and DNA Hybridization of a Diverse Set of Bacteria, Anal. Microchem. 181:23-27(1989) (microwave irradiation applied in filter lysis technique. Bollet et a. report enhanced lysis of Gram positive pathogens by applying microwave radiation during a standard detergent extraction procedure. A Simple Method for the Isolation of Chromosomal DNA from Gram Positive or Acid-fast Bacteria, Nucl. Acids Research 19:1955 (1991). Cheyrou et al. report exposing a 10 xcexcL serum sample to microwave radiation for 2-4 minutes, and using the desicated preparation directly for PCR analysis of Hepatitis B Virus. Improved Detection of HBV DNA by PCR after Microwave Treatment of Serum, Nucl. Acids Research 19:4006 (1991). Cheyrou et al. propose that the microwave radiation mediated the denaturation of serum-associated PCR inhibitory factors. In all of these studies microwave radiation was applied by placing the sample in a conventional microwave oven. Additionally, microwave irradiation has proved useful for achieving enhanced or more specific results in chemical reactions of many types. See, e.g., Whittaker, G., Fast and Furious, New Scientist, Feg. 28, 1998, p. 34-37.
Given the desire to conduct chemical reactions and processes in microfluidic devices (such as nucleic acid extraction, amplification and further processing thereof), there is a need in the art to improve the performance of these devices. Microwave radiation applied to chemical reactions and processes, including nucleic acid extraction from microorganisms, has proven to enhance, or sometimes make possible the desired result. Thus, there is a need in the art for microfluidic devices in which microwave radiation can be applied to the reaction cavities within the device.
The present invention is directed to a microfluidic device having a monolithic microwave integrated circuit (MMIC) for applying microwave radiation to a cavity within the microfluidic device. The MMIC may have a microstrip design, slot design, or a coplanar design. In one embodiment the MMIC is used for lysing cells, in other emodiments the MMIC is used to heat a sample.
The present invention also provides methods for lysing cells in a microfluidic device. The cells are introduced into a cavity within the device microwave radiation is applied to the cavity from a monolithic microwave integrated circuit. The method may further comprise separating a target analyte, for example and without limitation nucleic acid, from the lysate.